Question

Hydrogen peroxide can be prepared in several ways. One method is the reaction between hydrogen and oxygen, another method is the reaction between water and oxygen. Calculate the ΔG°rxn of each reaction below?

1) H2(g) + O2(g) <==> H2O2(l) ΔG°rxn=? (in kJ)
2) H2O(l) + 1/2O2(g) <==> H2O2(l) ΔG°rxn=? (in kJ)

Which method requires less energy under standard conditions?
Reaction 1
Reaction 2


I know reaction 1 is -120.4 kj and reaction 2 is 116.7 kj, but I'm not sure about the second part, will the second one require less energy because it has a positive energy?

Answer 1

Reaction 1 requires more energy because when delta G is a negative number you know your reaction is spontaneous.Just like when delta G is positive we know the reaction is non-spontaneous. If a reaction takes place spontaneously, it makes more sense for it to use less energy then a reaction that is non-spontaneous.

Answer 2

Its reaction 1.